Further investigations of raspberry bushy dwarf virus in New Zealand

New Zealand Journal of Crop and Horticultural Science ISSN: 114-71 (Print) 1175-8783 (Online) Journal homepage: https://www.tandfonline.com/loi/tnzc2 Further investigations of raspberry bushy dwarf virus in New Zealand G. A. Wood To cite this article: G. A. Wood (1995) Further investigations of raspberry bushy dwarf virus in New Zealand, New Zealand Journal of Crop and Horticultural Science, 23:3, 273-281, DOI: 1.18/11471.1995.9513899 To link to this article: https://doi.org/1.18/11471.1995.9513899 Published online: 22 Mar 21. Submit your article to this journal Article views: 1 Citing articles: 9 View citing articles Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalinformation?journalcode=tnzc2

New Zealand Journal of Crop and Horticultural Science, 1995, Vol. 23: 273-281 114-71/95/233-273 $2.5/ The Royal Society of New Zealand 1995 273 Further investigations of raspberry bushy dwarf virus in New Zealand G. A. WOOD The Horticulture and Food Research Institute of New Zealand Mt Albert Research Centre Private Bag 92 19 Auckland, New Zealand Abstract In a test of 3 red raspberry (Rubus idaeus L.), hybrid berry, and Boysenberry (R. ursinus Chamisso and Schlechtendal) selections, bred in New Zealand or imported from overseas in recent years, only two were found to be infected with raspberry bushy dwarf virus (RBDV). However, 18 were found to be susceptible to infection by graftinoculation with the virus. Results of graftinoculating eight New Zealand sources of RBDV to cultivars known to be susceptible to the resistance breaking strain (RBDV-RB), but immune to the common strain (RBDV-S), suggests that the resistance breaking strain is unlikely to be present in New Zealand. Testing for RBDV in a number of commercial Boysenberry plantings in the Nelson district, indicated that the virus was widespread there in this crop. In tests to produce an indicator for the leaf yellowing symptom of RBDV, 'Marion' blackberry (R. ursinus derivative) proved unreliable, but consistent vivid yellows on the red raspberry cultivar 'Autumn Britten' (formerly '37/') suggest it to be the best indicator yet found in New Zealand. The leaf yellows found on the cultivars 'Southland' and 'Taranaki' may be nontransmissible syndromes. Leaf symptoms were not found on Boysenberry following graft inoculation with RBDV, and the leaf symptoms caused by black raspberry necrosis virus (BRNV) were not accentuated when combined with RBDV. When H953 Received II January 1995; accepted 18 April 1995 thorny and thorn-free Loganberries (R. loganobaccus Bailey) were graft-inoculated with RBDV, no degeneration of growth was observed. Keywords Rubus; raspberry bushy dwarf virus disease; red raspberry; hybrid berry; Boysenberry selections; leaf yellowing symptoms; crumbly berry fruit symptoms INTRODUCTION In the early 197s, a leaf yellowing condition appeared in commercial plantings of red raspberry (Rubus idaeush.) in New Zealand. The most popular cultivars at the time, 'Lloyd George', 'Marcy', and 'Taylor' were affected, as were the lesser grown cultivars 'Canby' and 'Great American'. The leaf yellowing was in some instances accompanied by a crumbly berry condition of the fruit, particularly in 'Marcy' (Wood & Todd 197). The leaf yellows were at first thought to be caused by trace element deficiencies. As measures to correct these deficiences had no effect, red raspberry plants showing the symptom were tested for virus infection by mechanical inoculation of sap to herbaceous indicator hosts. A virus was found to be present in red raspberry plants showing the leaf yellows symptom, and subsequent surveys of the main red raspberry growing districts in 1975 and 197showed that this virus was widespread in red raspberry throughout New Zealand (Fry & Wood 1978). Leaf yellows had been reported in red raspberry in other countries (Cadman 1952; Daubeny et al. 1978), as had a virus which was thought to cause a bushy dwarf symptom in red raspberry (Cadman 193). Subsequent investigations showed that the bushy dwarf symptom was primarily caused by black raspberry necrosis virus (BRNV) (Jones 1979) which is unrelated to the virus which had been found in New Zealand associated with leaf yellows and crumbly fruit. Early uncertainties over the identity of the viruses associated with leaf yellows,

274 New Zealand Journal of Crop and Horticultural Science, 1995, Vol. 23 crumbly berry, and bushy dwarf symptoms, resulted in the name, raspberry bushy dwarf (RBDV), being applied to the virus responsible for crumbly berry and leaf yellows in red raspberries grown in New Zealand, even though it does not cause a bushy dwarf symptom. This name has also been used overseas for the same range of symptoms. Because of its debilitating effects on growth and fruit yield, RBDV is regarded as a serious disease of red raspberries (Wood &Todd 197; Murant 1987). As most of the red raspberry cultivars grown in New Zealand during the 197s were susceptible to RBDV, which spreads rapidly through infected pollen (Murant et al. 1974), the growing of cultivars immune to the virus was promoted (Wood & Todd 197). However, those of the 'Mailing' series from the United Kingdom which were immune to RBDV, did not perform well in New Zealand (Fry & Wood 1978). Of several immune North American cultivars tried since the 197s, 'Fairview' produced long laterals which were difficult to manage, and 'Willamette' suffered from poor budbreak. Some success was achieved with 'Heritage' as an autumn fruiting cultivar (Woodet al. 1991). Of the otherred raspberry cultivars imported during the early 198s and subsequently trialled in commercial plantings, some such as 'Autumn Bliss' and 'Glen Moy' proved commercially successful (Langford 1992). However, 'Autumn Britten' (formerly '37/') rapidly became infected with RBDV, and was so severely affected with leaf yellows and crumbly fruit that it ceased to be recommended as a commercial cultivar (Wood et al. 1991). A breeding programme was set up in New Zealand in the. 197s to produce red raspberry cultivars and hybrid berries suitable for growing conditions in this country (Hall & Brewer 1989). Some of these have subsequently shown great promise for New Zealand growing conditions (Hall 1992a b; Langford 1993). The breeding programme also had as one of its objectives the development of new cultivars which would be immune to RBDV (Hall 1992b). As RBDV is seed transmitted in red raspberry (Cadman 195; Murant et al. 1974), and some of the parent material used in the breeding programme was RBDV-infected, a testing programme was initiated for RBDV in progeny which showed the greatest commercial promise. Details of the work are outlined here, and this paper reports on: (1) testing newly imported, and locally bred selections of red raspberry, hybrid berry, and BoysenberryforpresenceofRBDV; (2) determining the susceptibility of those found free from RBDV by graft-inoculation with a known source of the virus; (3) investigating if the resistance-breaking strain of RBDV is present in New Zealand; (4) investigating the incidence of RBDV in Boysenberry in the Nelson district; (5) comparing 'Autumn Britten' and 'Marion' blackberry as RBDV leaf yellows indicators, and investigating other leaf yellowing symptoms in Rubus; () the combined effects of RBDV and BRNV in Boysenberry; and (7) the effects of RBDV in Loganberry. MATERIALS AND METHODS Occurrence of RBDV in imported and locally bred cultivars of red raspberry, hybrid berry, and selections of Boysenberry To improve the quality of Rubus types, a breeding programme has been in operation for a number of years (Hall & Brewer 1989). Together with several new cultivars imported from overseas breeding programmes, the New Zealand Rubus breeding programme has resulted in a number of new cultivars recently becoming available of red raspberry, hybrid berry, and selections of Boysenberry. As these cultivars had been grown for several years in areas where RBDV is known to occur, they were tested for presence of the virus. In spring, soft shoot growth was crushed in 2.5% nicotine and with the aid of carborundum abrasive, the inoculum mechanically inoculated to plants of Chenopodium quinoa Willd. and cucumber (Cucumis sativus L. 'Heinz Pickling'). Results of the tests were observed 7-14 days after inoculation. Susceptibility to RBDV by graft inoculation Those of the new selections which were found free from RBDV in the field were tested to determine if they were susceptible, by graft inoculation, to the strain of RBDV occurring in New Zealand, and to see if any would develop leaf yellows when infected. In late summer, container-grown single plants of each cultivar were graft-inoculated in the glasshouse with RBDV, using the inarch bottle grafting technique (Garner 1958). Bottles in which the scion bases were contained were kept filled with water for 4 weeks, before being removed. Any graft failures were regrafted. Single plants of each cultivar were left ungrafted as controls. The plants were transferred to the outdoors during the winter to al low dormancy to occur. In spring, soft shoot growth was removed and tested for presence of RBDV on herbaceous hosts as in the above trial. Floricane and primocane

Wood Raspberry bushy dwarf virus 275 leaves of the Rubus plants were observed for leaf yellowing symptoms. Testing for presence of the resistance breaking strain of RBDV (RBDV-RB) in New Zealand Because of concerns that the resistance breaking strain of RBDV (RBDV-RB) might be present in New Zealand, eight sources of RBDV in New Zealand were tested to determine if all were of the common strain (RBDV-S) (Jones 198), or if any were the RBDV-RB strain. The United Kingdom red raspberry cultivars 'Glen Clova' and 'Mailing Delight' are resistant to the RBDV-S strain, but susceptible to the RBDV- RB strain (Murant et al. 1982). As graft inoculation with RBDV-RB often kills or seriously affects 'Glen Clova' (Barbara et al. 1985), observation for these effects, and subsequent testing for infection can be used as a test method (Jones 198). Accordingly, in late summer the inarch bottle grafting technique was used to inoculate in the glasshouse plants of 'Glen Clova', and in some instances 'Mailing Delight'. The isolates were also grafted to 'Norfolk Giant' to observe expression of leaf yellows symptoms (Cadman 1952). Subsequent treatment of the grafted plants and herbaceous host testing was as in the above trial. Incidence of RBDV in Boysenberry in the Nelson district In early investigations, infection found in a single plant in the Wairarapa district indicated Boysenberry as a potential natural host of RBDV in New Zealand (Jones & Wood 1979). In a more recent investigation of the cause of a decline in crop yield of Boysenberry on a commercial planting in Nelson, RBDV infection was found to be widespread in this planting in both Boysenberries and Youngberries (R. ursinus derivative) (Wood et al. 1991), although there has not been any evidence to link the decline in yield to the presence of RBDV. Because of its importance as the major Boysenberry growing area of New Zealand (Langford & Mavromatis 1981), a survey was commenced in 1992 of a number of other commercial Boysenberry plantings in the Nelson district to see if the virus was present in them. To expand the investigation, limited tests were made of some commercial plantings in the Whakatane and Auckland districts. To test for infection, samples were taken from three to seven locations on each planting and tested on herbaceous indicators as in the above trials. Leaf yellows indicators In New Zealand, RBDV was first associated with a leaf yellowing of red raspberry in the 197s (Fry & Wood 1978), and later shown to be a causal agent of the symptom (Jones et al. 1982). Possibly because of the number of red raspberry cultivars commercially grown, and susceptible to the RBDV- S strain in New Zealand, leaf yellowing appears to be more widespread, more severe, and more consistent in occurrence than in Britain (Jones et al. 1982) and North America (Daubeny et al. 1978). The widespread appearance of leaf yellows in New Zealand red raspberry plantings became of major concern to growers, particularly as this was sometimes accompanied by dieback of the fruiting cane and crumbly berry of the fruit (Wood & Todd 197). As later investigations suggested that not all of the leaf yellowing was caused by RBDV, two new Rubus cultivars were trialled as leaf yellows indicators, and the new instances of yellowing in Rubus investigated. A single yellows affected plant of 'Marion' blackberry (R. ursinus derivative) was found on a commercial property at Hastings. Leaf symptoms were a conspicuous yellowing between the secondary veins (Fig. 1), or in some instances covering almost the entire leaf area. Unlike symptoms commonly occurring in red raspberry, which are pronounced only in spring and early summer, the symptoms on 'Marion' leaves would last the full season. Mechanical inoculation of sap to herbaceous indicator plants showed RBDV to be present in the 'Marion' plant. To determine if other sources of RBDV in New Zealand would induce the same symptom on 'Marion', those from 'F29', 'LloydGeorge', 'Marcy, 'OhauEarly', Youngberry, and from infected 'Marion' (for comparative purposes), were bottle grafted to container-grown 'Marion' plants which had been tested and found free from RBDV, and had never shown leaf yellows symptoms. The red raspberry cultivar 'Autumn Britten' was imported from the United Kingdom, and following a period in plant quarantine where it was tested and found free from RBDV and other diseases, was planted in 198 at Greytown in the Wairarapa district, an area where RBDV commonly occurs (Fry & Wood 1978). Within 2 years a number of plants of 'Autumn Britten' had developed conspicuous leaf yellowing symptoms and were shown by testing to be infected with RBDV (Wood et al. 1991). Leaf yellows symptoms on 'Autumn

27 New Zealand Journal of Crop and Horticultural Science, 1995, Vol. 23 Fig. 1 Rubus leaves with yellows symptoms: 'Marion' blackberry (R. ursinus derivative), top left; 'Autumn Britten' red raspberry (R. idaeus), top right; 'Taranaki' hybrid berry, bottom left; and 'Southland' red raspberry, bottom right. Fig. 2 Conspicuous leaf yellowing symptoms on container-grown raspberry bushy dwarf virusinfected 'Autumn Britten' red raspberry (Rubus idaeus) plant.

Wood Raspberry bushy dwarf virus 277 Britten' were the most vivid of those seen on red raspberry in New Zealand (Figs 1 and 2). As it was thought that 'Autumn Britten' could be useful as a leaf yellows indicator for RBDV, the New Zealand sources of RBDV from 'F29\ 'Lloyd George', 'Marcy', 'Marion', Youngberry, and also 'Autumn Britten' (for comparative purposes), were bottle grafted to healthy container-grown plants of 'Autumn Britten' to observe symptom expression. Marginal and veinal yellowing (Fig. 1) of the leaves of some fruiting laterals occurs on the recently developed hybrid berry 'Taranaki' (Hall 1992a). To see if RBDV was involved in this condition, samples were tested by mechanical inoculation to herbaceous indicators, to determine if RBDV was present. Similarly, a single plant of 'Southland' red raspberry was found on a commercial planting near Auckland with conspicuous marginal and veinal yellowing of the floricane leaves (Fig. 1). This was tested for the presence of RBDV by mechanical inoculation to herbaceous indicator plants, and bottle grafting to 'Norfolk Giant'. Combined effects of RBDV and BRNV in Boysenberry Past investigations both in New Zealand and in other countries have indicated that RBDV occurs without symptoms in Boysenberries (Converse 1973; Jones & Wood 1979). BRNV, which occurs in low incidence in red raspberries in New Zealand (Jones & Wood 1979) can cause a chlorotic mottle on leaves of Boysenberry (Jones & Jennings 198). BRNV has only rarely been found in Boysenberry in New Zealand, but it was thought advisable to determine what effects if any, there would be when this virus was combined with RBDV in Boy senberry. Several container-grown plants of 'Boysen 72' were bottle-grafted with both RBDV obtained from 'Autumn Britten' red raspberry, and BRNV obtained from 'ZevaHerbstente' red raspberry. Single plants of 'Boysen 72' were grafted with RBDV, and with BRNV for comparative purposes. The plants in their containers, together with non-grafted 'Boysen 72' control plants were placed outdoors in late autumn, and examined for leaf symptoms in the following spring and early summer. RBDV and Loganberry degeneration In early investigations into RBDV, the virus was thought to be associated with a degenerative condition of Loganberries (Barnett & Murant 197; Ormerod 1972). More recent testing in England of the thorny Loganberry ('LY59'), and thorn-free Loganberry ('L54'), found both to be widely infected with RBDV-RB, but neither showed any apparent symptoms (Barbara et al. 1985). Both 'LY59' and 'L54' are present in New Zealand, having been imported from East Mailing Research Station, England, in 192 and 198 respectively (HortResearch Plant Quarantine records). Both have been tested and found free from RBDV. To determine any effects of RBDV on 'LY59' and 'L54' in New Zealand, container-grown plants of them were bottlegrafted with RBDV-infected red raspberry. The plants in their containers, together with non-grafted control plants were placed outdoors in late autumn, and examined for signs of degeneration in the spring and early summer of the following two seasons. RESULTS Occurrence of RBDV in Rubus Results of testing the new red raspberry cultivars for RBDV showed that only two, 'Ohau Early' and 'F29' were infected (Table 1). None of the hybrid berries and Boysenberry/hybrid berry selections were infected. Susceptibility by graft inoculation Results of graft-inoculation tests showed that three of the red raspberries were susceptible to the strain of RBDV occurring in New Zealand (Table 1). Of the hybrid berry and Boysenberry selections 15 were susceptible. Four of these developed leaf yellowing in late summer of the season which followed graft inoculation (Table 1). Testing for the resistance breaking strain RBDV could not be detected by herbaceous indicator host tests in any of the 'Glen Clova' plants grafted with eight sources of RBDV (Table 2). Nor were there any visible symptoms of RBDV on the 'Glen Clova', although the plant grafted with the 'Marcy' source of RBDV demonstrated that it was also infected with raspberry leaf spot virus by producing visible leaf symptoms (Jones 1987). No infection of RBDV was found in any of the grafted 'Mailing Delight' plants, nor were any symptoms seen on them. All sources of RBDV grafted to 'Norfolk Giant' tested positive for the virus when mechanically inoculated to herbaceous indicator hosts, and all of the 'Norfolk Giant' plants showed leaf yellows symptoms.

278 New Zealand Journal of Crop and Horticultural Science, 1995, Vol. 23 RBDV in Boysenberry RBDV was found to be widespread in Boysenberries in the Nelson district (Table 3). No infection was found in Whakatane, and only a small amount of infection was detected in Auckland. Leaf yellows indicators All grafted plants of 'Marion' blackberry were found to be RBDV infected when tested in the season following graft inoculation. Some reduction in growth occurred, and several sources of RBDV induced leaf yellowing on the 'Marion' but not conspicuously, and not until several seasons after inoculation. All sources of RBDV grafted to 'Autumn Britten' infected the cultivar, and induced conspicuous leaf yellowing on it in the following season. RBDV could not be detected in 'Taranaki' and 'Southland' by mechanical inoculation of sap to herbaceous indicator hosts. Nor was any infection found in, or leaf yellows symptoms seen on, 'Norfolk Giant' plants following grafting with 'Southland'. RBDV and BRNV in Boysenberry Testing by mechanical inoculation of sap to herbaceous indicator hosts of the Boysenberries graft-inoculated with RBDV, confirmed that they were infected with the virus. Boysenberries graftinoculated with BRNV produced undersized floricane leaves with light green areas around the mid-rib and main veins. Leaf symptoms on the plant grafted with BRNV alone, was the same as that on the BRNV and RBDV infected plants. There were Table 1 New Rubus cultivars found naturally infected with raspberry bushy dwarf virus (RBDV) (Column 1), the response of others to graft inoculation with the virus (Column 2), and the expression of leaf yellows (Column 3). (+, infected; -, not infected; =, not tested; Y, leaf yellows; *, may be a non-transmissible condition.) Red raspberries Chilliwack Clutha(BC74-ll-41) Comox Ohau Early Rakaia Selwyn Waiau (R1) F29 8492P2 M82 N4.4 (1) (2) (3) Hybrid berries - + Kaiteri (BCB8) - - Mahana(815M17) - - Ranui (833158) + = Y Riwaka Tahi (832F74) - + Taranaki (821C93) 8443W2 - - 8531V + = 89L.3 - - 81L1.3 - + 825N-8 - - 827N8-828M14-5 829O14-2 871D.4 (1) (2) (3) _ + - - + + - * - _ - - + + + - - Boysenberry selections (1) (2) (3) Nectar _ + C4 - Li2 - + L3 - + Wl - + Table 2 Response of raspberry bushy dwarf virus resistance breaking strain (RBDV-RB) infectable Rubus cultivars to New Zealand isolates of raspberry bushy dwarf virus (RBDV), and effects of the isolates on 'Norfolk Giant'. (+, infected; -, not infected; =, not tested; Y, leaf yellows.) Isolate source Glen Clova Boysenberry, Nelson F29 raspberry, Motueka - Lloyd George, Motueka Marcy, Motueka - Marion blackberry, Hastings Ohau Early, Hamilton Youngberry, Nelson - Autumn Britten raspberry, Wairarapa Mailing Delight _ = = = - - - - Norfolk Giant

Wood Raspberry bushy dwarf virus 279 no leaf symptoms on the Boysenberry grafted with RBDV alone. RBDV in Loganberry Testing by mechanical inoculation of sap to herbaceous indicator plants of the Loganberries 'LY59' and 'L54' graft-inoculated with RBDV, confirmed that they were infected with the virus, but neither showed any sign of degeneration over a 2-year period in comparison to the control plants. DISCUSSION Because of its debilitating effects on growth and fruit yield, RBDV is regarded as a serious disease of red raspberries in New Zealand (Wood & Todd 197; Murant 1987). As the RBDV leaf yellowing sympton had not been reported on red raspberries before 197, it is unlikely that the virus was present here much before that date. It is probable that RBDV was introduced to New Zealand with the importation of a new and infected Rubus cultivar in the mid-late 19s, shortly before adequate plant quarantine virus screening proceedures were adopted in the early 197s (Fry & Wood 1978; Wood 1989). The practise of evaluating new Rubus cultivars in the various growing districts of New Zealand would have enabled a RBDV-infected cultivar to widely distribute the virus. In the field, honey bees are the most likely vector of RBDV (Bulger et al. 199). The rapid spread in New Zealand in cultivars such as 'Autumn Britten' may be the result of the higher light intensities and warmer spring temperatures of the southern hemisphere red raspberry growing areas, encouraging a greater bee activity than would occur in northern hemisphere plantings. Thus it is unfortunate the grafting tests have demonstrated that a number of the newly developed red raspberries, hybrid berries, and Boysenberry selections of the New Zealand breeding programme are susceptible to infection, as is the new importation 'Chilliwack'. It is possible, as found in the United Kingdom, that some cultivars will not become infected with RBDV when grown for extended periods in the field (Barbara etal. 1984; Jennings & Jones 1989). Of the cultivars which have been found to be resistant to RBDV, the New Zealand bred 'R1' ('Waiau') has the resistant 'Fairview' as one parent (Hall 1992b), and '8492P2' the resistant 'Haida' (Jenning& Jones 1989) as one parent (Hall pers. comm.). These parents are likely to have conferred RBDV resistance to 'R1' and '8492P2'. It is unfortunate that the hybridberry '827N8-' is one of the those susceptible to RBDV, as it has shown great promise for future commercial use in New Zealand (Langford 1994). Results of the tests with the eight New Zealand sources of RBDV suggests that only the RBDV-S type strain is present in New Zealand, probably originating from a single infected imported cultivar, and that the RBDV-RB strain is unlikely to occur here. It is also unlikely that a third strain of RBDV, which occurs in black raspberries in North America (Murant & Jones 197; Murant et al. 1982) is present in New Zealand, as black raspberries are not grown in New Zealand as a commercial crop (Langford 1988). With these strains of RBDV being absent from New Zealand, development of red raspberry cultivars resistant to the RBDV-S strain will be the main priority for the future. Some testing in several districts for RBDV in Boysenberries, the most important Rubus crop in New Zealand (Langford & Mavromatis 1981), had been carried out in the 197s, but at the time only one instance of infection had been found (Jones & Wood 1979). It is therefore surprising that so much infection has been found in the Nelson district in the present survey. Some spread of infection will have occurred through the dissemination of infected Table 3 Nelson properties No. of plants tested No. infected Presence of raspberry bushy dwarf virus (RBDV) in Boysenberry (Rubus ursinus) plantings. Whakatane properties No. of plants tested No. infected Auckland properties No. of plants tested No. infected A 3 A A 1 B 4 B C 3 1 C D 7 7 E F 4 G 4 H I J 1 K 1 L 3

28 New Zealand Journal of Crop and Horticultural Science, 1995, Vol. 23 propagation material. However, as RBDV is known to spread via infected pollen in Loganberries (Cadman 195), a closely related species, it is probable that this has occurred also in Boysenberry. As reported in North America (Converse 1973), and in New Zealand (Jones & Wood 1979) (also this paper), Boysenberries do not show any obvious leaf symptoms, but on one of the properties affected in Nelson, the grower concerned believes it is possible to differentiate between healthy and RBDV-infected plants by the yield of the fruit. This is an area requiring further investigation. Jones et al. (1982) noted that the leaf yellowing of RBDV infected red raspberry was greatly influenced by environmental factors, and that its occurrence was particularly prevalent in New Zealand. Until the present, although a number of the older cultivars grown in New Zealand are known to show symptoms, the United Kingdom cultivar 'Norfolk Giant' has been used as the standard leaf yellowing indicator. The vivid and consistent symptoms on 'Autum Britten' when graft-inoculated with RBDV make it a reliable indicator that may in future supersede 'Norfolk Giant' for this purpose. 'Marion' blackberry has also been considered for this purpose, but its erratic symptom expression when grafted with RBDV make it unsuitable. As to why the original plant of 'Marion' shows vivid yellows throughout the season, whereas graftinoculated 'Marion' plants initially show little or no yellows is not known, but it appears that with 'Marion' the more conspicuous yellows are not apparent until several years after infection. The possibility that the yellowing on 'Marion' leaves is caused by the combined effects of RBDV and blackberry calico, a disease common in trailing blackberries in western North America (Wilhelm et al. 1951; Converse 1987) has been considered. However, the chlorotic veinal line patterns described on 'Marion' when affected by calico (Jones et al. 199; Jones et al. 1992) have not been observed in New Zealand 'Marion'. Nor have the chlorotic areas occurred on leaves of Boysenberry (Converse 1987) or thorny Loganberry, following graftinoculation with 'Marion'. Thus the blackberry calico disease, which has never been reported in New Zealand, would not appear to be involved. The yellowing found in the foliage of 'Taranaki' and 'Southland' demonstrates that not all Rubus leaf yellowing can be attributed to RBDV. However, close examination of the leaves of both 'Taranaki' and 'Southland' shows the symptoms to be in the form of marginal chlorosis extending into and clearing the secondary veins, as compared to the interveinal chlorosis normally expressed on susceptible cultivars by RBDV. Grafting tests completed to date indicated that the 'Southland' yellowing is a non-transmissible syndrome, and the same may apply for 'Taranaki'. The trial with Boysenberries indicated that graft inoculation with RBDV does not cause foliage symptoms, and that the symptoms caused by BRNV are not accentuated by a combination of the two viruses. The results of graft-inoculating Loganberries with RBDV showed, as found in the United Kingdom, that this virus is not involved in Loganberry degeneration. ACKNOWLEDGMENTS H. K. Hall of The Horticulture and Food Research Institute of New Zealand Limited orchard at Riwaka, Motueka, for supply of samples from the Rubus breeding programmes. REFERENCES Barbara, D. J.; Ashby, S. C.; Knight, V. H. 1985: The occurrence and distribution of isolates of raspberry bushy dwarf virus in England. Annals of applied biology 1: 75-81. Barbara, D. J; Jones, A. T.; Henderson, S. J.; Wilson, S. C.; Knight, V. H. 1984: Isolates of raspberry bushy dwarf virus differing in Rubus host range. Annals of applied biology 15: 49-54. Barnett, O. W.; Murant, A. F. 197: Host range, properties and purification of raspberry bushy dwarf virus. Annals of applied biology 5: 435-449. Bulger, M. A.; Stace-Smith, R.; Martin, R. R. 199: Transmission and field spread of raspberry bushy dwarf virus. Plant disease 74: 514-517. Cadman, C. H. 193: Affinities of viruses infecting fruit trees and raspberry: Plant disease reporter 47: 459-42. Cadman, C. H. 195: Filamentous viruses infecting fruit trees and raspberry and their possible mode of spread. Plant disease reporter 49: 23-232. Converse, R. H. 1973: Occurrence and some properties of raspberry bushy dwarf virus in Rubus species in the United States. Phytopathology 3: 78-783. Converse, R. H. 1987: Blackberry calico. Pp. 245-24 in: Virus diseases of small fruits. United States Department of Agriculture handbook no. 31. 277 p. Daubeny, H. A.; Stace-Smith, R.; Freeman, J. A. 1978: The occurrence and some effects of raspberry bushy dwarf virus in red raspberry. Journal of the American Society for Horticultural Science 13: 519-522.

Wood Raspberry bushy dwarf virus 281 Fry, P. R.; Wood, G. A. 1978: Two berry fruit virus diseases newly recorded in New Zealand. New Zealand journal of agricultural research 21: 543-547. Garner, R. J. 1958: Bottle grafts. The grafters handbook. East Mailing Research Station. 2 p. Hall, H. K. 1992a: Hybridberry breeding DSIR research to improve the Boysenberry. The orchardist of New Zealand 5: 18-2. Hall, H. K. 1992b: Raspberry breeding a promise of life for a struggling industry. The orchardist of New Zealand 5: 32-33. Hall.H. K.; Brewer, L.R. 1989:Breedingi?Rubus cultivars for warm temperate climates. Acta horticulture 22: 5-72. Jennings, D. L.; Jones, A. T. 1989: Further studies on the occurrence and inheritance of resistance in red raspberry to a resistance-breaking strain of raspberry bushy dwarf virus. Annals of applied biology 114: 311-323. Jones, A.T. 1979: The effects of black raspberry necrosis and raspberry bushy dwarf viruses in Lloyd George raspberry and their involvement in raspberry bushy dwarf disease. Journal of horticultural science 54: 27-272. Jones, A. T. 198: Advances in the study, detection and control of viruses and virus diseases of Rubus, with particular reference to the United Kingdom. Crop research (horticulture research) 2: 127-171. Jones, A. T. 1987: Raspberry leaf mottle and raspberry leaf spot. Pp. 183-187 in: Virus diseases of small fruits. United States Department of Agriculture handbook no. 31. 277 p. Jones, A. T.; Jennings, D. L. 198: Genetic control of the reactions of raspberry to black raspberry necrosis, raspberry leaf mottle, and raspberry leaf spot viruses. Annals of applied biology 9: 59-5. Jones, A. T.; McGavin, W. J.; Watkins, C. A. 1992: Recent studies in Scotland on the aetiology of virus and virus-like diseases of small fruit crops. Acta horticulturae 38: 31-35. Jones, A. T.; Mitchell, M. J.; McGavin, W. J.; Roberts, I. M. 199: Further properties of wineberry latent virus and evidence for its possible involvement in calico disease. Annals of applied biology 117: 571-581. Jones, A. T.; Murant, A. F. Jennings, D. L.; Wood, G. A. 1982: Association of raspberry bushy dwarf virus with raspberry yellows disease; reaction of Rubus species and cultivars, and the inheritance of resistance. Annals of applied biology 1: 135-147. Jones, A. T.; Wood, G. A. 1979: The virus status of raspberries (Rubus idaeus L.) in New Zealand. New Zealand journal of agricultural research 22: 173-182. Langford, G. I. 1988: Raspberries are red, yellow and black. The New Zealandfruit and produce journal (New Zealand Fruit and Produce Merchants and Auctioneers Federation) (Nov/Dec). P. 15. Langford, G. I. 1992: Variety review. The orchardist of New Zealand 5: 39. Langford, G. I. 1993: Variety review. New Zealand commercial grower 48: 28. Langford, G. I. 1994: Season review. New Zealand commercial grower 49: 25-2. Langford, G. I.; Mavromatis, G. 1981: A review of the Boysenberry industry. Report of the New Zealand Ministry of Agriculture & Fisheries. Murant, A. F. 1987: Raspberry bushy dwarf. Pp. 229-234 in: Virus diseases of small fruits. United States Department of Agriculture handbook no. 31. 277 p. Murant, A. F.; Chambers, J.; Jones, A. T. 1974: Spread of raspberry bushy dwarf virus by pollination, its association with crumbly fruit, and problems of control. Annals of applied biology 77: 271-281. Murant, A. F.; Jones, A. T. 197: Comparison of isolates of raspberry bushy dwarf virus from red and black raspberries. Acta horticulturae : 47-51. Murant, A. F.; Jones, A. T.; Jennings, D. L. 1982: Problems in the control of raspberry bushy dwarf virus. Ada horticulturae 129: 77-88. Ormerod, P. J. 1972: Rubus virus investigations; Loganberry. In: Report of the East Mailing Research Station for 1971. P. 127. Wilhelm, S.; Thomas, H. E.; Koch, E. C. 1951: Diseases of the Loganberry. California agriculture 5: 11, 14. Wood, G. A. 1989: Propagation, virus-screening and heat therapy of northern hemisphere imports of Ribes, Rubus, and Vaccinium. New Zealand journal of crop and horticultural science 17: 271-274. Wood, G. A.; Langford, G. I.; Fletcher, J. D. 1991: Raspberry bushy dwarf virus in New Zealand. The orchardist of New Zealand 4: 28-3. Wood, G. A.; Todd, J. C. 197: Crumbly berry and leaf yellows in raspberry. New Zealand commercial grower 31: 3, 23.